Moir\'e Magnetic Exchange Interactions in Twisted Magnets

TL;DR

This paper develops a microscopic model for moiré magnetic exchange interactions in twisted van der Waals magnets, revealing new magnetic skyrmion bubbles and controlling their properties via twist angle and substrate effects, advancing spintronic applications.

Contribution

The authors introduce a novel microscopic moiré spin Hamiltonian and demonstrate its ability to predict and control moiré magnetic exchange interactions and related spin textures in twisted magnets.

Findings

Discovery of moiré-type skyrmion bubbles with non-conversed helicity.

Control of skyrmion size and population through twist angle.

Manipulation of magnetic phases via substrate-induced Dzyaloshinskii-Moriya interaction.

Abstract

Besides moir\'e superlattice, twisting can also generate moir\'e magnetic exchange interactions (MMEIs) in van der Waals magnets. However, due to the extreme complexity and twist-angle-dependent sensitivity, all existing models fail to capture the MMEIs, preventing the understanding of MMEIs-induced new physics. Here, we develop a microscopic moir\'e spin Hamiltonian that enables the effective description of MMEIs via a sliding-mapping approach in twisted magnets, as demonstrated in twisted bilayer CrI3. Unexpectedly, we discover that the emergence of MMEIs can create an unprecedented magnetic skyrmion bubble (SkB) with non-conversed helicity, named as moir\'e-type SkB, representing a unique spin texture solely generated by MMEIs and ready to be detected under the current experimental conditions. Importantly, the size and population of SkBs can be finely controlled by twist angle, a key step for skyrmion-based quantum computing and information storage. Furthermore, we reveal that the MMEIs can be effectively manipulated by the substrate-induced interfacial Dzyaloshinskii-Moriya interaction, modulating the twist-angle-dependent magnetic phase diagram, which solves the outstanding disagreements between prior theories and experiments and verifies our theory.